A battery is usually initially charged by using a constant current till its voltage reaching a preset upper limit. Next, the charging mode will be immediately changed to the constant-voltage mode. During this charging mode, the battery voltage is held at the previous preset voltage limit, whereas the charging current will be gradually decreased to a preset lower limit. Once the charging current is dropped to the lower current limit, the whole charging processes will be definitely completed.
During the above-mentioned charging process, the state of degradation or aging of a battery is never considered. Undoubtedly, the degradation or aging of a battery can seriously deteriorate its performances and functions. As a result, a charging method that can complete the charging mission without damaging any performances or functions of a battery, will be the best choice. Nevertheless, in the conventional applications, a high preset current in the constant-current mode is usually used in order to acquire more electricity in a shorter charging time. It inevitably results in the premature decay of a battery due to high temperature effects, including the non-uniform temperature distribution with an over-preset difference between upper and lower limit values, the rise of the over-upper-limit temperature, the rise of the excessive change rates of temperature, and the local thermal concentration.
Additionally, there are the other four factors that significantly affect the life span of a battery, i.e. charging and discharging under lower limit of temperature, charging over upper limit of voltage, discharging under lower limit of voltage, and charging and discharging over the upper limit of current. In view of the above, there is still room to provide a better battery charging method.